1. Field of the Invention
The present invention concerns a method and a device for determining the physical characteristics of a semiconductor material. The method is of a type comprising the following consecutive steps:
removably applying a wafer of said material to the base of an insulative container having a hole in the base so as to cover said hole,
placing an electrolyte in said container so that a first side of said wafer constituting a working electrode is in contact with said electrolyte,
disposing an auxiliary electrode in said electrolyte opposite said working electrode,
connecting a direct current electrical power source between a second side of said wafer and said auxiliary electrode, and
determining the characteristics of the wafer by examining said first side.
2. Description of the Prior Art
A method of this type is disclosed in French Patent Application No. FR-A-2.344.847 (IBM). In this method, a semiconductor wafer is applied to the external wall of the base of a container formed with a hole, so as to close off this hole. The hole is fitted with a ring on which the wafer bears. The wafer is held against the ring by a stainless steel component bearing on the base of the container. An electrolyte based on hydrofluoric acid is disposed in the container. The two terminals of an electrical power source are connected respectively to the stainless steel component, this component being in contact with the wafer which serves as a main electrode, and to a platinum film immersed in the electrolyte and which serves as an auxiliary electrode.
The method described in the aforementioned French patent is limited to the detection of electrically active defects in an N type silicon substrate. Moreover, this method has disadvantages. The usable area of the wafer is delimited by that of the hole in the container. Moreover, the adjustment of the pressure of the ring on the wafer raises difficult problems, notably when the wafer is thin: insufficient pressure may result in defective sealing of the container, whereas excessive pressure may break the wafer. Note also that the stainless steel component disposed between the wafer and the power source entails the risk of introducing stray voltage drops which could falsify certain measurements.
A general objective of the present invention is to overcome these disadvantages.